1. Field of the Invention
The present invention relates to a liquid application apparatus, a liquid storage method and an inkjet recording apparatus, and more particularly to a liquid application apparatus, a liquid storage method and an inkjet recording apparatus which apply a liquid taken from a tank, onto a medium.
2. Description of the Related Art
An inkjet recording apparatus comprising a mechanism that applies a liquid to a recording medium with the object of quickening the aggregation of pigment when recording with inks that use pigments for colorants are well known in the field of inkjet recording apparatuses. Japanese Translation of PCT Application No. 2002-517341 discloses accumulation of a coating liquid between a roller and a doctor blade and supply of the coating liquid to the roller as the roller rotates. Then, in Japanese Translation of PCT Application No. 2002-517341, as the roller to which the coating liquid has been applied rotates, the supplied coating liquid is transferred and applied to a support member that is transported between this roller and another roller. Japanese Patent Application Publication No. 8-72227 also indicates a mechanism in an inkjet recording apparatus for applying a treatment liquid that makes dye insoluble onto recording paper prior to recording. Example 1 of Japanese Patent Application Publication No. 8-72227 discloses that the treatment liquid present in a supplementary tank is discharged by adhering to a rotating roller, and the discharged treatment liquid is applied to the recording paper.
Nonetheless, both of the configurations disclosed in the above Japanese Translation of PCT Application No. 2002-517341 and Japanese Patent Application Publication No. 08-72227 supply or feed the application liquid onto the surface of a rod bar or roller based on the rotation of the rod bar or roller, and the part of the application liquid that is supplied or fed is exposed to or is in communication with the atmosphere. For that reason, in addition to such problems as evaporation of the application liquid, there is the possibility that leakage of the application liquid will occur if the positioning of the apparatus is changed. Specifically, when considering leakage of liquid caused by positioning changes during transport of an inkjet recording apparatus such as a printer, it is difficult to utilize the application mechanisms disclosed in Japanese Translation of PCT Application No. 2002-517341 and Japanese Patent Application Publication No. 8-72227 in a small-scale apparatus.
To address these problems, Japanese Patent Application Publication No. 2005-254809 discloses a mechanism that seals the part that supplies the application liquid to the roller. In the application mechanism described in Japanese Patent Application Publication No. 2005-254809, the member that supplies liquid to the roller is configured by providing a ring-shaped elastic roller abutment member on one surface of the space forming base member. Based on this configuration, when the roller abutting member abuts the application roller by the energizing force of a spring member or the like, abutment along the circumferential shape of the application roller is enabled, and abutment with uniform pressure is realized. As a result, this becomes a substantially sealed space based on one surface of the space forming base member and the circumferential surface of the application roller, and the application liquid is maintained in this space. Then, when rotation of the application roller has stopped, the abutment member and the circumferential surface of the application roller are maintained in a sealed liquid state, and leakage of liquid to the outside is prevented.
In this regard, in Japanese Patent Application Publication No. 2005-254809 a pump is provided between the tank for the purpose of storing the application liquid and the application mechanism, and by using this pump to suction the application liquid of the application mechanism, the ink is recovered into the tank from the application mechanism, moreover, the ink is suctioned into the application mechanism from the tank by negative pressure generated by the application mechanism. In this way, in between operations of the apparatus, the pump causes the application liquid to flow, and when printing ends, the application liquid in the application mechanism and the tube is recovered into the tank, evaporation of the application liquid and generation of increased viscosity and adhesion of the application liquid is thereby prevented. However, this does not mean that all liquid in the tube can be completely recovered, and some remains in the supply channel and the recovery channel. For example, liquid may remain on the wall surfaces of the supply and recovery channels, which are cylindrical tubes, inside the changeover valve, on wall surfaces of the liquid holding member, inside the pump, and the like. Specifically, liquid is prone to remain on the wall surfaces of the liquid holding member, inside the changeover valve, and inside the pump because these parts incorporate mechanisms. The evaporation of the liquid remaining inside the apparatus, such as in the supply channel and the pump, will progress until liquid is supplied in the next filling process. Then, the viscosity of the liquid increases as evaporation progresses. As the viscosity of the liquid increases, the liquid becomes paste-like (also called viscous substance), and can become a solid of solidified liquid (also called solidified substance). When liquid is filled the next time, the paste-like liquid hinders the flow of liquid in the flow channels because the viscosity is higher than that of normal liquid. Moreover, if viscosity has increased in the application mechanism, the new liquid that could be filled without increased viscosity and the viscous liquid simultaneously slip through the nip part, and differences in the thickness of the liquid that has slipped through may appear because of the differences in the respective surface tensions. For this reason, application unevenness may appear on the application medium. Moreover, if solidified substance in generated, clogging in the channels through which the liquid circulates may occur. In this way, viscous substance and solidified substance may cause the supply and recovery of liquid to be unsatisfactory. Moreover, application of liquid to the application medium may not be conduced with high quality.
Japanese Patent Application Publication No. 2006-167556 discloses an apparatus that provides in at least one of the application liquid supply and recovery channels an avoidance space Q that maintains separation of viscous substance and solidified substance from application fluid, and prevents inhibition of satisfactory supply and ejection of application liquid in the application liquid chamber, flow channels, and pump when the apparatus is stopped for long periods of time, and when application liquid has evaporated, increased in viscosity and solidified in the supply channel. Here, even when providing this kind of avoidance space, over long-term use the avoidance space may be evaded allowing viscous substance and solidified substance to slip through, or the avoidance space may become full thereby inhibiting satisfactory supply and ejection of application liquid and producing adverse effects such as application unevenness. Consequently, stability during long-term use, and countermeasures to increased viscosity and solidification of the application fluid caused by evaporation and the like have been sought.